This proposal involves characterization of the mode of metabolic inhibition of mannose on the sucrose-supported growth of Azotobacter vinelandii under N2-fixing conditions. Preliminary data indicate that this type of inhibition is specific for sucrose and turanose and is influenced by the nitrogen status of the cells. This inhibition could be modulated by calcium, certain cyclic nucleotides and a factor secreted by this organism. The goals of this proposal include the construction of the catabolic pathway of mannose by radioisotope tracing of 14C-mannose intermediates on paper electrogram. Specific enzymes and co-factors required for mannose transport and catabolism will be purified and characterized using established methods such as differential centrifugation, column chromatography etc. Additionally, the effect of mannose on sucrose-specific catabolic enzymes, such as the permease and the invertase, will be elucidated. Mutants that are not sensitivity of mannose inhibition will be isolate to facilitate and confirm this study. The long term goal is to understand how Ca, cyclic nucleotides and other factors influence the nitrogen control and regulate cell growth. This study could provide new information on cell growth and cell regulation in bacteria.